1. Field of the Invention
This invention provides a new use for an old product, namely a novel way to prevent the transmission of bluetongue virus from the Culicoides gnat to sheep by treating the skin of the sheep and, more particularly the skin upon the back of the sheep to a chemotherapeutic dosage of sulfamoyl phenyl esters of organic phosphates.
2. Description of the Prior Art
The raising of sheep for both wool and food is an important industry in the United States, as well as in many other countries. This industry is currently being threatened by a viral disease known as bluetongue. Bluetongue was first reported in United States in 1952 but already is felt responsible for the decimation of the Big Horn sheep population of West Texas in 1967. While the effects of bluetongue are largely felt in the domesticated sheep industry, the disease can attack any ruminant with mortality being documented following disease outbreaks in mule deer, antelope, Big Horn sheep, as well as cattle. Death losses from bluetongue is usually in the 10-30% range. Abortion, early embryonic death, and malformed lambs are also a result of the disease. Another great economic loss caused by the disease is the loss of weight of feeder lambs and young sale rams which contract the disease. Another common occurrence due to the disease is the sterilization of rams for a period of up to six months following recovery from the disease even though the disease may have been mild. Sterilization may be permanent in more severe cases. Obviously, this problem can lead to late lambs or no lambs in small flocks.
The bluetongue virus is carried from one animal to another by a small gnat called Culicoides. When the gnat bites an infected animal it acquires the virus and carries it to the next animal it feeds on. Presently, there are two approaches to controlling the gnat to prevent disease. The first is to reduce the breeding sites of the gnat and the second is use of chemical pesticides. Presently there are no pesticides registered for gnat control and therefore reducing the breeding areas is the most important method. Draining stagnant pools of water significantly reduces or eliminates the breeding site of the gnats. Spraying breeding sites to control gnats is proven not economically feasible. It has been shown that even if all gnats are killed in one area, by the next day new ones move in from surrounding areas. Heretofore, there has not been an effective method for controlling transmission of the bluetongue disease.
Sulfamoylphenyl esters of organic phosphates have been used for controlling parasites attacking warm blooded animals as disclosed and claimed in U.S. Pat. No. 3,179,560 issued to R. I. Hewitt. Such esters have been found to be very effective systemic insecticides for destroying the parasites. As shown in the same patent, the compound has been found effective against gastrointestinal nematodes in sheep. In the treatment of nematodes, the compound was given orally.